In the energy systems models used to generate the scenarios reported here,
the entire energy systems structure is represented from primary energy extraction,
through conversion, transport, and distribution, all the way to the provision
of energy services. Primary energy harnessed from nature (e.g., coal from a
mine, hydropower, biomass, solar radiation, produced crude oil, or natural gas)
is converted in refineries, power plants, and other conversion facilities to
give secondary energy in the form of fuels and electricity. This secondary energy
is transported and distributed (including trade between regions) to the point
of final energy use. Final energy is transformed into useful energy (i.e., work
or heat) in appliances, machines, and vehicles. Finally, application of useful
energy results in delivered energy services (e.g., the light from a light bulb,
mobility).

Box 4-9: Dynamics of Technological Change in the MESSAGE-Based Quantifications
for the Four SRES Marker Scenarios.

Technological change in energy supply and end-use technologies has historically
been a main driver of structural changes in energy systems, efficiency
improvements, and improved environmental compatibility. Yet, despite its
crucial role, the mechanisms that underlie technological innovation and
diffusion of new technologies remain poorly understood, so modeling technological
change as an endogenous process to the economy and society is still in
its infancy. Historically, the track record of technology forecasts has
at best been mixed, with a number of notable failures particularly in
the energy sector. In the 1960s, for instance, R&D in the US attempted
to develop nuclear-propelled aircraft, and nuclear electricity was anticipated
to become "too cheap to meter." Conversely, the dynamic technological
changes in microprocessors, information technologies, and aeroderivative
turbines (and their combination with the steam cycle in the form of combined
cycle gas turbines) were largely underestimated. This is similar to the
pessimistic market outlook for gasoline-powered cars at the end of the
19th and start of the 20th centuries.

In recognition of the considerable uncertainty in describing future technological
trends, a scenario approach was adopted to vary technology-specific assumptions
in the MESSAGE model runs of the SRES scenarios. Depending on the specific
interpretation of the four SRES scenario storylines, alternative technologies
and alternative ranges of their future characteristics were assumed as
model inputs.

Two guiding principles determined the choice of particular technology
assumptions in MESSAGE.

First, technologies not yet demonstrated to function on a prototype scale
were excluded. Therefore, for instance, nuclear fusion is excluded from
the technology portfolio of all SRES scenarios calculated with the MESSAGE
model. However, production of hydrogen- or biomass-based synfuels (e.g.
ethanol) or advanced nuclear and solar electricity generation technologies
are included, as they have demonstrated their physical feasibility at
least on a laboratory or prototype scale, or in some specific niche markets
(even if they are uneconomic at currently prevailing energy prices). Second,
the range of technology-specific assumptions is empirically derived. Statistical
distributions of technology characteristics based on a large technology
inventory (consisting of 1600 technologies) and developed at IIASA (Messner
and Strubegger, 1991; Strubegger and Reitgruber, 1995) were used. Means,
maxima, and minima from these distributions (e.g. of estimated future
technology costs) guided which particular values to adopt across scenarios
on the basis of the scenario taxonomy suggested by the scenario storylines
(ranging from conservative to optimistic).

Tables 4-13a to 4-13e summarize the technology characteristics and resultant
diffusion rates across the four SRES scenario families and their scenario
groups. Table 4-13a presents a brief overview of a selection of major
energy technologies represented in the MESSAGE model. (Being a detailed
"bottom-up" model, MESSAGE literally contains hundreds of individual technologies,
too many to summarize here; instead, only the most important technology
groups, aggregated across many individual technologies, are presented.)
Table 4-13b summarizes salient technology characteristics in terms of
levelized costs (investment and operating costs levelized per unit energy
output, excluding fuel costs) and Table 4-13c summarizes the resultant
marker deployment (diffusion) of these technologies by 2050 and 2100 for
the B2-MESSAGE marker scenario. This scenario is characterized by intermediate
levels of growth in energy demand and conservative assumptions as to future
technological change. The latter were adopted based on a literature survey
(Strubegger and Reitgruber, 1995) as well as an expert opinion poll.

In particular, the B2-MESSAGE scenario adopted technology characteristics
of the equally conservative IIASA-WEC Scenario B (Nakicenovic et al.,
1998), which was based on the Strubegger and Reitgruber (1995) analysis,
complemented by a review of some 100 energy experts assembled by WEC.
Table 4-13d indicates how technology costs in the other MESSAGE scenarios
differ from those of the B2 scenario. (The prevalence of negative values
in Table 4-13d indicates that most scenarios are more optimistic concerning
cost improvements of future technology than the MESSAGE B2 scenario.)
Finally, Table 4-13e indicates the difference in market deployment (diffusion)
of the other MESSAGE SRES scenarios compared to that of the B2 scenario.
Positive values indicate higher market deployment, and negative ones show
lower diffusion. However, differences across scenarios in terms of technology
diffusion are not governed by technology costs alone. Other technology
characteristics (such as efficiency and infrastructure availability) and
market (demand) growth are also important in determining market deployment
rates and diffusion potentials of energy technologies.

Table 4-13d: Levelized costs (1990US$/ GJ)
of selected energy technologies (excluding fuel costs) in MESSAGE
scenarios relative to the costs in the B2- MESSAGE marker scenario
(minima and maxima for eleven world regions). The A1C and A1G scenario
groups have been combined into the fossil- intensive A1FI group in
the SPM (see also footnote
1).

2050

2100

B1

A1B

A1C

A1G

A1T

A2a

B1

A1B

A1C

A1G

A1T

A2a

min

max

min

max

min

max

min

max

min

max

min

max

min

max

min

max

min

max

min

max

min

max

min

max

Coal conversion

0

0

0

0

0

0

0

0

0

0

-0.6

0

0

0

0

0

0

0

0

0

0

0

-0.6

0

IGCC

-0.8

-1.1

-0.6

-0.8

-0.6

-0.8

1.1

0.8

-0.6

-0.8

-0.8

-0.3

0.0

-1.7

0.3

-1.1

0.8

-0.8

2.5

0.8

0.3

-1.1

0

-0.6

Coal fuel cell

-2.2

-2.2

-2.2

-2.2

-2.2

-2.2

-0.3

-0.3

-2.2

-2.2

0

0

-2.5

-2.5

-2.5

-2.5

-2.5

-2.5

-0.3

-0.3

-2.5

-2.5

0

0

Oil

-1.1

0

-1.1

0

0

0

-1.1

0

-1.1

0

0.3

-0.6

-1.1

0

-1.1

0

0

0

-1.1

0

-1.1

0

0.3

-0.6

Gas standard

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NGCC

-1.4

-0.6

-1.4

-0.6

-0.3

0.6

-1.1

-0.6

-1.1

-0.6

-0.3

0.6

-0.8

0

-0.8

0

0.3

1.1

-0.6

0.0

-0.6

0

0

1.1

NGFC

-1.4

-1.4

-1.4

-1.4

0

0

-1.1

-1.1

-1.4

-1.4

0

0

-2.2

-2.2

-2.2

-2.2

0

0

-1.1

-1.1

-2.2

-2.2

0

0

Biofuel

-0.6

-1.7

-0.6

-1.7

0.0

0.0

-0.3

-1.1

-0.6

-1.7

0

0

-1.4

-2.8

-1.4

-2.8

0

0

-0.3

-1.1

-1.4

-2.8

0

0

Nuclear

0

0

0

0

1.4

0

0

0

0

0

0

0

0

0

0

0

1.4

0

0

0

0

0.0

0

0

Advanced nuclear/other

-2.2

0.6

-3.9

0.6

-1.1

3.3

-1.1

1.9

-3.6

0.6

0

0

-5.3

2.2

-6.4

-2.5

-2.2

3.3

-2.2

-0.3

-5.8

-1.4

0

0

Hydro

0

0

0

0

0

0

0

0

0

0

0.3

-5.6

0

0

0

0

0

0

0

0

0

0

0.3

-5.6

Wind

-2.8

-2.8

-4.7

-4.7

3.3

3.3

-2.8

-2.8

-4.7

-4.7

0.0

0.6

-4.2

-4.2

-6.4

-6.4

3.3

3.3

-2.8

-2.8

-6.4

-6.4

0.0

0.6

Other renewables

-3.3

-2.8

-4.4

-2.8

0.8

12.8

-3.9

-2.8

-4.4

-2.8

0.8

13.3

-5.3

-2.8

-6.1

-2.8

0.8

12.8

-4.2

-2.8

-6.1

-2.8

0.8

10.8

Hydrogen fuel cell

-1.3

-1.3

-1.2

-1.2

0

0

-0.9

-0.9

-1.5

-1.5

0

0

-2.1

-2.1

-1.8

-1.8

0

0

-0.8

-0.8

-2.3

-2.3

0

0

Photo-voltaic

-4.2

-5.8

-5.3

-7.5

8.1

11.9

0.0

0.0

-5.3

-7.5

0.6

11.1

-6.1

-5.8

-6.7

-9.4

8.1

11.9

0.0

0.0

-6.7

-9.4

0.6

11.1

Coal synliquids

-1.3

-1.8

-1.7

-0.9

-2.1

-0.9

-1.7

-0.9

-1.7

-0.9

-1.3

-0.9

-1.3

-1.8

-1.7

-0.9

-2.4

-0.9

-1.7

-0.9

-1.7

-0.9

-1.3

-0.9

Bio synliquids

-1.7

-1.7

-1.7

-1.7

0.0

0.0

-0.8

-0.8

-1.7

-1.7

0.0

0.0

-2.4

-1.7

-2.3

-1.7

0.0

0.0

-0.8

-0.8

-2.4

-1.7

0.0

0.0

Gas synliquids

-0.5

-0.5

1.1

1.1

0.0

0.0

1.0

1.0

1.1

1.1

0.0

0.0

-0.8

-0.5

1.1

1.1

0.0

0.0

1.0

1.0

1.1

1.1

0.0

0.0

Syngases

-0.5

-1.0

-0.5

-1.0

0.0

-0.5

-0.5

0.6

-0.5

-1.0

0.0

0.0

-0.6

-1.0

-0.5

-1.0

0.0

-0.5

-0.5

0.6

-0.6

-1.0

0.0

0.0

Hydrogen H2(1)

-0.3

-0.7

-0.3

-0.7

0.8

1.6

-0.3

-0.6

-0.3

-0.7

0.0

0.0

-0.7

-0.7

-0.7

-0.7

0.8

1.6

-0.3

-0.6

-0.7

-0.7

0.0

0.0

Hydrogen H2(2)

0.0

-0.4

-0.2

-0.4

0.3

1.4

0.0

-0.3

-0.2

-0.4

0.0

0.0

0.0

-0.4

-0.5

-0.4

0.1

1.4

0.0

-0.3

-0.5

-0.4

0.0

0.0

Hydrogen H2(3)

-3.0

-1.6

-5.0

-7.4

5.5

1.3

-8.4

-12.6

-5.0

-2.3

7.1

8.6

-3.0

-1.6

-5.5

-7.4

5.5

1.3

-8.4

-12.6

-5.5

-2.3

7.1

8.6

A. Cost variations refer to a four- region model only.
The spread across regions is therefore somewhat smaller than in the
other scenarios.

Table 4- 13e: Energy output (EJ) of selected
energy technologies in MESSAGE scenarios relative to the B2- MESSAGE
marker scenario. The A1C and A1G scenario groups have been combined
into the fossil- intensive A1FI group in the SPM (see also footnote
1).

2050

2100

B1

A1B

A1C

A1G

A1T

A2a

B1

A1B

A1C

A1G

A1T

A2a

Coal conversion

-8.6

6.5

36.0

26.9

4.7

16.9

0.0

1.8

6.5

7.5

0.1

7.2

IGCC

-15.6

8.8

-4.7

-2.9

-12.3

25.2

-65.1

-26.3

-17.6

-65.1

-65.1

62.7

Coal fuel cell

0.0

2.2

12.9

2.4

0.0

0.0

0.0

0.1

204.9

0.0

0.0

0.0

Oil

0.0

0.0

0.0

7.8

0.0

0.0

0.0

0.0

0.0

1.0

0.0

0.0

Gas standard

-0.3

-0.3

-0.3

3.8

0.7

-0.3

0.0

0.0

0.0

0.0

0.0

0.0

NGCC

-15.1

34.4

-7.7

13.0

5.5

-18.1

-64.7

102.8

-67.8

143.4

-43.5

-2.0

NGFC

-5.1

10.0

10.3

26.2

-1.6

-3.6

0.0

0.0

0.0

60.5

0.0

0.0

Biofuel

-2.2

5.0

6.7

12.1

0.4

-0.5

-19.1

55.3

-19.3

-13.4

-15.9

3.9

Nuclear

-13.1

-9.2

-11.1

-5.3

-11.3

13.4

-50.0

-41.2

-50.6

-22.5

-50.6

31.2

Advanced nuclear/other

-4.0

44.8

83.6

47.2

44.8

-14.7

-52.0

255.0

253.5

211.1

16.2

-38.4

Hydro

0.4

8.7

7.2

7.3

3.5

1.4

-3.6

11.3

12.5

8.2

-2.6

3.8

Wind

-0.2

5.5

-0.6

2.5

4.4

1.7

-7.9

14.6

1.7

1.9

0.3

1.0

Other renewables

1.9

9.2

-12.8

3.0

8.5

-10.0

3.8

21.2

-10.4

2.0

18.8

7.2

Hydrogen fuel cell

57.0

5.2

-10.5

9.8

41.3

-8.7

84.2

92.7

-11.4

28.5

309.7

-9.4

Photo-voltaic

-1.8

12.9

8.5

14.2

9.7

-2.9

-29.3

58.3

42.2

45.9

34.3

-0.4

Coal synliquids

1.2

34.7

177.0

29.3

24.8

48.4

-69.4

-57.0

421.3

-48.9

-57.7

258.0

Biomass synliquids

-5.6

-30.4

1.3

-30.7

-22.2

-17.1

-9.0

-34.6

-6.5

7.9

-20.4

34.9

Gas synliquids

-3.3

-3.2

24.7

-6.5

-5.3

-5.1

-27.9

-33.1

137.3

-5.1

-29.1

64.0

Syngases

0.5

6.4

2.0

0.5

-0.1

0.5

60.6

854.7

84.3

0.0

990.2

35.6

Hydrogen H2(1)

75.2

-8.4

-24.3

45.9

-6.5

-15.2

0.0

0.0

0.0

0.0

0.0

0.0

Hydrogen H2(2)

17.3

-5.6

-9.6

-10.1

-9.5

-5.8

0.0

0.0

0.0

0.0

0.0

0.0

Hydrogen H2(3)

62.7

97.9

5.1

0.0

125.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

A. Calculated with a four- region model. The spread
across regions is therefore somewhat smaller than in the other scenarios.

Important differences exist in accounting conventions on how to calculate the
primary energy equivalent of particularly renewable and nuclear energy (see
Watson et al., 1996). To assure comparability of model results, the SRES writing
team agreed to adopt as a common accounting methodology the direct equivalent
method for all non-thermal uses of renewables and nuclear. The primary energy
equivalence of these energy forms is accounted for at the level of secondary
energy, that is, the first usable energy form or "currency" available to the
energy system. For instance, the primary energy equivalence of electricity generated
from solar photo-voltaics or nuclear power plants is set equal to their respective
gross electricity output, not to the heat equivalent of radiation energy from
fissile reaction, the solar radiance that falls onto a photo-voltaic panel and
is converted into electricity with efficiencies that range from 10% to 15%,
or the heat that would have to be generated by burning fossil fuels to produce
the same amount of electricity as generated in a photo-voltaic cell or a nuclear
reactor (as used in the so-called "substitution" accounting method). This common
33
SRES accounting convention must be borne in mind when comparing the primary
energy-use figures of this report with those of other studies, which invariably
use different accounting methods depending on the organization that produces
the scenario. An illustration of the sensitivity of different accounting methods
on estimates of primary energy use in long-term energy scenarios is given in
Nakicenovic et al. (1998). (See also the discussion in Chapter
2, in which scenario comparisons are based on index numbers rather than
absolute figures to account for these definitional differences.)

Table 4-14:Primary energy use (EJ) for the four SRES
marker scenarios and all SRES scenarios in 1990, 2020, 2050, and 2100. The
range for 1990 illustrates the differences in base-year calibration across
the models and uncertainties that stem from the inclusion or exclusion of
non-commercial energy use, which is particularly important for developing
countries.

2050

2100

Region

1990

A1

A2

B1

B2

A1

A2

B1

B2

OECD90

151-182

267
(184-315)

266
(207-300)

166
(134-233)

236
(189-236)

397
(181-607)

418
(267-496)

126
(126-274)

274
(197-274)

REF

69-95

103
(83-267)

93
(57-116)

64
(50-79)

97
(53-117)

139
(70-290)

155
(61-457)

39
(25-80)

125
(40-328)

IND

227-252

370
(303-532)

359
(264-406)

230
(203-303)

334
(255-339)

536
(275-896)

573
(385-847)

164
(164-345)

399
(237-593)

ASIA

49-79

440
(293-789)

335
(249-449)

272
(204-537)

319
(284-411)

838
(308-965)

581
(477-753)

154
(154-434)

521
(309-562)

ALM

35-49

538
(235-634)

278
(166-354)

312
(176-312)

217
(137-254)

852
(391-1109)

563
(437-662)

196
(196-446)

437
(300-538)

DEV

84-123

977
(606-1278)

612
(415-740)

583
(406-837)

536
(421-660)

1639
(700-2074)

1144
(914-1375)

350
(350-880)

959
(609-1096)

WORLD

326-368

1347
(913-1611)

971
(679-1059)

813
(642-1090)

869
(679-966)

2226
(1002-2737)

1717
(1304-2040)

514
(515-1157)

1357
(846-1625)

Table 4-14 gives an overview of primary energy use in the four SRES marker
scenarios and the range of all SRES scenarios.

Figure 4-11: Global primary energy structure,
shares (%) of oil and gas, coal, and non-fossil (zero-carbon) energy sources
- historical development from 1850 to 1990 and in SRES scenarios. Each
corner of the triangle corresponds to a hypothetical situation in which
all primary energy is supplied by a single source - oil and gas, coal
at the left, and non-fossil sources (renewables and nuclear) to the right.
Constant market shares of these energies are denoted by their respective
isoshare lines. Historical data from 1850 to 1990 are based on Nakicenovic
et al. (1998). For 1990 to 2100, alternative trajectories show the changes
in the energy systems structures across SRES scenarios. They are grouped
by shaded areas for the scenario families A1, A2, B1, and B2 with respective
markers shown as lines. In addition, the four scenario groups within the
A1 family (A1, A1C, A1G, and A1T) that explore different technological
developments in the energy systems are shaded individually. The A1C and
A1G scenario groups have been merged into one fossil-intensive A1FI scenario
group in the SPM (see footnote
1). For comparison the IS92 scenario series are also shown,
clustering along two trajectories (IS92c,d and IS92a,b,e,f). For model
results that do not include non-commercial energies, the corresponding
estimates from the emulations of the various marker scenarios by the MESSAGE
model were added to the original model outputs.

Figure 4-11 illustrates both the historical change of world primary energy
structure over time and future changes as given in the SRES scenarios. Each
corner of the triangle corresponds to a hypothetical situation in which all
primary energy is supplied by a single source - oil and gas at the top, coal
at the left, and non-fossil sources, renewables (including wood), and nuclear
at the right. The historical change reflects major technology shifts from the
traditional use of renewable energy flows to the coal and steam age of the 19
th century, and subsequently to the dominance of oil and internal combustion
engines in the 20 th century. In around 1850 (lower right of Figure 4-11), only
about 20% of world primary energy was provided by coal; the other 80% was provided
by traditional renewable energies (biomass, hydropower, and animal energy).
With the rise of industrialization, coal substituted for traditional renewable
energy forms, and by 1910 (lower left of Figure 4-11) around three-quarters
of world primary energy use relied on coal. The second major transition was
the replacement of coal by oil and later by gas. By the early 1970s (see 1970
point labeled on Figure 4-11), 56% of global primary energy use was based on
oil and gas. From the early 1970s to 1990, the global primary energy structure
has changed little, although efforts to substitute for oil imports have led
to an increase in the absolute amount of coal used and to the introduction of
non-fossil alternatives in the OECD countries (e.g., nuclear energy in France).
Rapid growths in energy demand and coal use, particularly in Asia, have outweighed
structural changes in the OECD countries.

Figure 4-11 also gives an overview of the evolution of the global energy system
between 1990 and 2100 as reflected in the SRES scenarios. The four marker scenarios
are shown as thick lines. In addition, for each scenario family the area spanned
by all the SRES scenarios in that family is marked in the same color as the
trajectory for the respective marker. The SRES scenarios cover a wider range
of energy structures than the previous IS92 scenario series, reflecting advances
in knowledge on the uncertainty ranges of future fossil resource availability
and technological change. Scenarios B1, B2, A1T, and to some extent A1B follow
a trend toward increasing shares of zero-carbon options in the long term. A1G
more or less follows an oil-gas isoshare line that perpetuates the current dominance
of oil and gas in the global energy balance far into the 21st century. Scenarios
in group A1C indicate a near doubling of coal's share in primary energy use.
Also of interest is the trajectory of the A2 marker scenario, which returns
in its energy structure by 2100 (over 50% coal share) to the situation that
prevailed almost 200 years before (i.e., around 1900). However, even with similar
fuel shares, the technologies, end-use fuels, and applications projected in
the A2 scenario are radically different from those of the past.